1. Field of the Invention
The present invention relates to a cam having a trimming function capable of setting and varying a photographic image plane size during photography.
2. Description of the Related Art
Two kinds of image plane sizes have mainly been provided in the field of conventional still cameras; a full size (24 mm.times.36 mm) and a half size (17 mm.times.24 mm). However, recently, a new size which is called a panorama size (13 mm.times.36 mm) has also been provided. Since the width of the panorama size is 36 mm, i.e., equal to the width of the full size, it is not necessary to apply a substantial modification to a mechanism for transporting film by one frame at one time. Accordingly, it is possible to realize photography of panorama size by covering an exposure opening for full-size photography by a required amount.
A camera has already been proposed which includes a built-in, movable light blocking member for the purpose of enabling panorama-size photography. The proposed camera is arranged to cover all exposure opening by a required amount in accordance with an operation performed by a photographer. The arrangement of this camera is schematically shown in FIG. 18. The shown arrangement includes a photographic optical system 101, an exposure opening 102 having a size corresponding to the full size, a hole 103 provided in a plane having the exposure opening 102, and light blocking members 104 and 105 provided above and below the exposure opening 102. The respective light blocking members 104 and 105 are turnable about shafts 104a and 105a, and are rotationally urged by means (not shown) to cover upper and lower portions of the exposure opening 102. The shown arrangement also includes an operating member 106 which is supported slidably in the upward and downward directions as viewed in FIG. 18, and the operating member 106 is arranged to be held at each of the upper and lower ends of its sliding stroke by a click mechanism (not shown). The shown state indicates that the operating member 106 is held at its upper click position. The operating member 106 includes an operating projection 106a, a cam portion 106b engageable with an operating projection 104b of the light blocking member 104, and a projection 106c engageable with a first arm 107b of a lever 107. The lever 107 is supported turnably about a hole 107a, and has the first arm 107b and a second arm 107c engageable with a projection 105 b of the light blocking member 105. The shown state indicates that the light blocking members 104 and 105 are respectively held at their retracted positions relative to a photographic optical path against an urging force due to a spring or the like by a click force applied by the operating member 106. When the light blocking members 104 and 105 are held in the shown state, if the photographer loads a film and executes photography, full-size photography is carried out. If the photographer slides down the operating member 106 before loading the film, the light blocking members 104 and 105 are respectively made to turn toward the left and the right to cover the upper and lower portions of the exposure opening 102. When the light blocking members 104 and 105 are in the state of covering the upper and lower portions of the exposure opening 102, if the photographer loads the film and executes photography, panorama-size photography is carried out.
The reason why the operating member 106 for size switching is disposed on one side of the exposure opening 102, i.e., at the position where the operating member 106 can be operated only before the film is loaded, is to allow the photographer to perform either one of full-size exposure and panorama-size exposure over the entire film. According to this arrangement, in a processing laboratory, when printing service of a processed film is to be performed, it is possible to transfer the film to a dedicated printing process in accordance with which of the full-size exposure and the panorama-size exposure has been performed.
In the field of lens-shutter types of cameras or the like, it has recently been proposed to provide a camera having a layout in which a size-switching operating member is disposed on the exterior face of the camera so that either of the full-size exposure and the panorama-size exposure can be selected during photography using one film.
However, the above-described related example has the following disadvantages.
(a) In the case of a camera having a focal plane shutter, since the focal plane shutter is disposed in front of the exposure opening of a camera body, it is difficult to dispose turnable light blocking members, an operating member and an associated interlocking mechanism, such as those used in the above-described related example. PA1 (b) In the camera having the focal plane shutter, since a plurality of shutter blades positioned in front of a film are each made from an extremely thin film and are arranged in overlapped form, if any variation occurs in the overlapped state of the shutter blades, light passing through a photographic lens may leak from between the shutter blades and expose the film. PA1 (c) In any of the above-described cameras, during photography, particularly during long-time photography (a low shutter speed), if image-plane-size setting means operates, an underexposure will occur in part of an image plane. PA1 (d) In the camera having the focal plane shutter, since the focal plane shutter is disposed in front of the exposure opening of the camera body, when a back lid is opened, the extremely-thin-film shutter blades of the focal plane shutter are exposed. During film loading, the exposed shutter blades may be soiled due to dust, moisture or the like and the accuracy of shutter operation may be degraded. Otherwise, the shutter blades may be broken by a hand or a leader portion of a film. PA1 (e) In any of the above-described cameras, during special photography, particularly during multiple exposure photography or automatic exposure bracketing photography, if the image-plane-size setting means operates, an underexposure will occur in part of the image plane. Otherwise, since image plane sizes do not become the same during, for example, the automatic exposure bracketing photography, it is impossible to attain the proper effect of the automatic exposure bracketing photography.